Researchers Predict Quieter Hurricane Season Than Usual
March 28, 2012

Researchers Predict Quieter Hurricane Season Than Usual

Colorado State University (CSU) researchers announced this week that the upcoming Atlantic hurricane season will be a quieter one.

The season, which begins on June 1, is predicted to have less than the average six hurricanes seen.

"A warming tropical Pacific and a cooling tropical Atlantic are leading us to think that the 2012 Atlantic hurricane season will have less activity" than average, meteorologists Philip Klotzbach and William Gray wrote in an online report.

"The tropical Atlantic has anomalously cooled over the past several months, and it appears that the chances of an El Niño event this summer and fall are relatively high," they said.

The El Niño weather phenomenon is a periodic warming of the tropical Pacific Ocean, suppressing hurricane activity in the Atlantic.

About six Atlantic hurricanes formed in the 2011 season, the worst being Irene, killing dozens of people and causing over $7 billion in damages.

The CSU researchers said they anticipate four possible scenarios for tropical cyclone activity, which were outlined by the team in December.

They wrote that there was a 5 percent chance of an unusually strong hurricane season, and no El Nino event, and a 25 percent chance of an above-average season with no El Nino.

They said the chances are higher, 45 percent, for an El Nino development, and a slightly lower hurricane season.  Under this scenario, there could be anywhere between 4 to 6 hurricanes, 1 to 2 of which could be major hurricanes.

"However, we stress the need to realize that there is inherent uncertainty in seasonal TC prediction." the authors wrote in the publishing.  "In addition, hurricanes can make landfall in inactive seasons and do major damage."

In December, the CSU team predicted a more active 2012 hurricane season, with a possibility of 7 to 9 hurricanes and 3 to 4 major hurricanes.  Since this prediction, El Nino seems to be becoming a more likely scenario, lessening the activity of the hurricane season.

The average hurricane per season data is based on data from 1981 to 2010.  The researchers also give a forecast parameter from 1950 to 2000 in their report.

Hurricane activity in the past 60 years has increased, according to the researcher's December report.  Their old climatology baseline from 1950 to 2000 had an average of 9.6 named storms per year, and 5.9 hurricanes.

Under the current climatology baseline, the CSU team said that there has been an average of 12 named storms in a hurricane season, as well as an average of 6.5 hurricanes.

Despite the increase in activity, major hurricanes under the old climatology baselines were slightly more often than those seen under the 1981 to 2010 baseline.

CSU said that an average of 2.3 major hurricanes a year took place between 1950 and 2000, compared to an average of 2.0 between 1981 and 2010.

The storm damages seen from the old climatology baseline is higher than the new baseline as well,  with an Accumulated Cyclone Energy of 96, compared to the new climatology at 92.

CSU researchers also said El Niño has historically had less active hurricane years.  They said years with El Niño have seen an average of 4.5 hurricanes and 9.5 named storms, compared to 7 hurricanes and 12 named storms for those years which have not had El Niño.

The researchers said that a detailed forecast for the 2012 hurricane season will be available on April 4.  They said this discussion will include predictions for numbers of named storms, hurricanes, major hurricanes, and more.


Image Caption: Hurricane Irene over the southern Bahamas on August 24. Credits: NASA image courtesy Jeff Schmaltz, MODIS Rapid Response, NASA Goddard Space Flight Center.